The proposed preliminary study specifically aims to 1.) test hypothesis that glucose can reverse memory deficits in older patients with more and less severe cognitive impairment, 2.) address age-related effects on glucose-induced alterations in cognitive functioning by comparison of younger and older groups of patients with schizophrenia, and 3.) further define the dose-response relationship between glucose administration and cognitive performance in schizophrenia by comparision of two oral glucose doses to placebo.